The present invention relates to a safety system of a boiling clothes washing machine for processing clothing with boiling or hot water, and particularly, to a safety control system of a boiling clothes washing machine and a system control method thereof for accurately detecting the temperature of wash water and the temperature of a heater to promote the safety of the system.
FIG. 1 is an illustrative example showing a number of safety devices installed on the bottom surface of a tub in accordance with the present invention, but it is referred to herein because it facilitates an explanation of the background art as well. A conventional washing machine includes a heater 2 mounted between the inner bottom of the tub 1 and the outer bottom of a wash tank 7. The tub 1 includes a metal bracket 3 which projects upward through the bottom surface of the tub 1 with a tight seal being kept between the bracket 3 and the bottom surface of the tub 1. The lower portion of the metal bracket 3 has a recess in the form of a box to receive a thermistor Th.sub.1 and a thermostat 36. The heater 2 is always in contact with the upper surface of the bracket 3 in a manner to be immersed. Therefore, the thermistor Th.sub.1 and the thermostat 36 detect the temperature of wash water and the heater to enable the heater 2 to be controlled. That is, the temperature detected by the thermistor Th.sub.1 is first compared to the temperature of the wash water and then to the temperature of the heater 2 to control the operation of the heater 2. If it is determined that the thermistor Th.sub.1 is out of order or has malfunctioned, the thermostat 36 is then required to control the operation of the heater 2.
A conventional safety apparatus only detects the surface temperature of the metal bracket 3, which is taken to be the temperature of the wash water. However, a large error arises between the actual and detected temperatures of the wash water due to the intervening thermal transferring medium, which in this case is the metal bracket 3. For example, the thermistor Th.sub.1 may sense that the surface temperature of the metal bracket 3 has increased by about 95.degree. C., causing the power source of the heater 2 to be cut off. However, the actual temperature of the wash water at this point is normally about 50.degree. C. As a result, the conventional washing machine launders clothing with only warm water. The warm water is not expected to wash terribly dirty clothes at the desired optimal cleaning level. It is known through user's experience that the boiling clothing process, in which terribly dirty clothes are allowed to stand in hot water of over 95.degree. C., is a very effective cleaning method. Therefore, it is necessary to accurately detect whether the temperature of wash water is over 95.degree. C.
Thus, it is a main object of the present invention to provide a safety control system and method of a boiling clothes washing machine for accurately detecting the actual temperature of the wash water, controlling a heater based on the detected temperature and performing the boiling wash at a very high temperature.
It is another object of the present invention to provide a safety control system and method of a boiling clothes washing machine for preventing a heater from over-heating while washing clothes with boiling or hot water.